Improved process and device for making aqueous wellbore treating fluids

Abstract

A device and a process for making aqueous treatment fluids for recovering crude oil from subterranean, oil-bearing formations, comprising water-soluble polymers, preferably polyacrylamides, by firstly diluting an aqueous polymer concentrate comprising 3.5 to 10 wt. % of water-soluble polymer with an aqueous base fluid to a concentration of 0.01 to 2 wt. % of the water-soluble polymer. And secondly, dosing the diluted aqueous polymer concentrate into a blender or a polymer injection unit to obtain an aqueous treatment fluid. The aqueous treatment fluids obtained may be used as fracturing fluids or as enhance oil recovery fluids, among others. Furthermore, a new aqueous polyacrylamide concentrate—and its preparation process—, which may be used as starting material for making aqueous treatment fluids. The new aqueous polyacrylamide concentrate comprises at least water, polyacrylamide, a salt and a polyol or a surfactant.

1 .- 37 . (canceled) 
     
     
         38 . Process for making an aqueous treatment fluid comprising water-soluble polymers for treating subterranean formations, characterized in that the process comprises, at least, the steps
 (I) diluting an aqueous polymer concentrate with an aqueous base fluid,   (II) mixing the diluted aqueous polymer concentrate of step (I) with additional aqueous base fluid, thereby obtaining the aqueous treatment fluid for treating subterranean formations,   wherein step (I) is carried out by means of a device comprising at least
 at least one source ( 1 ) for an aqueous base fluid, 
 at least one source ( 4 ) for an aqueous polymer concentrate, 
 a tube ( 2 ) for connecting the source(s) ( 1 ) with the inlet of a first pump ( 3 ), wherein the tube ( 2 ) additionally comprises an inlet ( 7 ) for adding the aqueous polymer concentrate to a stream of the aqueous base fluid, 
 a second pump ( 6 ), whose inlet side is connected with the source ( 4 ) for the aqueous polymer concentrate and whose pressure side is connected with the inlet ( 7 ), 
 a first pump ( 3 ), whose inlet side is connected with the tube ( 2 ), and whose outlet side is connected with a device for narrowing the cross-section ( 8 ), 
 a device for narrowing the cross-section ( 8 ), whose inlet side is connected with the first pump ( 3 ), and whose outlet side is connected with an outlet ( 15 ), 
 an outlet ( 15 ) for removing a diluted aqueous polymer concentrate from the device for further processing or using, 
   wherein step (I) comprises at least the sub-steps   (I-1) continuously sucking a stream of the aqueous base fluid from the at least one source ( 1 ) by means of the first pump ( 3 ),   (I-2) continuously adding a stream of the aqueous polymer concentrate comprising 3.5 to 10 wt. % of a water-soluble polymer, relating to the total of all components of the aqueous polymer concentrate, from the at least one source ( 4 ) to the stream of the aqueous base fluid by adding the concentrate into the inlet ( 7 ), by means of the second pump ( 6 ), thereby obtaining a stream of a mixture of the aqueous base fluid and the aqueous polymer concentrate,   (I-3) pressing the mixture obtained in (I-2) through the device for narrowing the cross-section ( 8 ) by means of the first pump ( 3 ), thereby generating a pressure difference, and   (I-4) continuously removing a stream of the diluted aqueous polymer concentrate comprising a concentration of the water-soluble polymer in the range of 0.01 to 2 wt. %, relating to the total of all components of the diluted aqueous polymer concentrate, through the outlet ( 15 ),   wherein the pressure difference generated when the stream of diluted aqueous polymer concentrate passes through the device for narrowing the cross-section ( 8 ) is in the range of from 6.9×10 5  to 1.1×10 6  Pa.   
     
     
         39 . Process according to  claim 38 , wherein the pressure is measured before the stream enters the device for narrowing the cross-section ( 8 ) and after the stream exist the device for narrowing the cross-section ( 8 ). 
     
     
         40 . Process according to  claim 38 , wherein the device additionally comprises a bypass ( 16 ), whose inlet side is connected with the connecting tube ( 2 ) between the at least one source ( 1 ) and the first pump ( 3 ) at a location before the inlet ( 7 ), and whose outlet side is connected with the connecting tube between the source ( 4 ) and the second pump ( 6 ), so that a part of the aqueous base fluid is added to the aqueous polymer concentrate before second pump ( 6 ). 
     
     
         41 . Process according to  claim 38 , wherein the diluted aqueous polymer concentrate comprises a concentration of the water-soluble polymer of 0.25 to 2 wt. %, relating to the total of all components of the diluted aqueous polymer concentrate. 
     
     
         42 . Process according to  claim 38 , wherein the aqueous polymer concentrate comprises
 40 to 94.5 wt. % of water,   3.5 to 10 wt. % of polyacrylamide,   1 to 25 wt. % of a polyol or a surfactant, and   1 to 25 wt. % of a salt   
       wherein the weight percentages relate to the total of all components of the aqueous polyacrylamide concentrate. 
     
     
         43 . Process according to  claim 42 , wherein the aqueous polymer concentrate comprises,
 70 to 90.5 wt. % of water,   3.5 to 10 wt. % of polyacrylamide,   3 to 10 wt. % of a polyol or a surfactant, and   3 to 10 wt. % of a salt   
       wherein the weight percentages relate to the total of all components of the aqueous polyacrylamide concentrate. 
     
     
         44 . Process according to  claim 42 , wherein
 the polyol is selected from polyethylene glycol, diethylene glycol, propylene glycol, sorbitol, mannitol and glycerol, or   the surfactant is selected from alkyl polyglucosides, carboxylated alkyl polyglucosides, alkoxylated alkylphenols, and polyethyleneoxide-polypropylenoxide block copolymers, and   the salt is selected from sodium chloride, potassium chloride, calcium chloride, magnesium chloride, magnesium sulfate, sodium sulfate, sodium phosphate and choline chloride.   
     
     
         45 . Process according to  claim 42 , wherein the aqueous polymer concentrate has been prepared by a step (0), which comprises, at least, the sub-steps:
 (i) mixing an aqueous polyacrylamide concentrate or a polyacrylamide gel with a polyol or surfactant solution,   (ii) homogenizing the mixture obtained in sub-step (i),   (iii) adding a salt solution.   
     
     
         46 . Device for making an aqueous treatment fluid comprising water-soluble polymers for treating subterranean formations, characterized in that the device comprises at least
 at least one source ( 1 ) for an aqueous base fluid,   at least one source ( 4 ) for an aqueous polymer concentrate,   a tube ( 2 ) for connecting the at least one source ( 1 ) with the inlet side of a first pump ( 3 ), wherein the tube additionally comprises an inlet ( 7 ) for adding the aqueous polymer concentrate to a stream of the aqueous base fluid,   a second pump ( 6 ), whose inlet side is connected with the source ( 4 ) for the aqueous polymer concentrate and whose pressure side is connected with the inlet ( 7 ),   a first pump ( 3 ), whose inlet side is connected with the tube ( 2 ), and whose outlet side is connected with a device for narrowing the cross-section ( 8 ),   a device for narrowing the cross-section ( 8 ), whose inlet side is connected with the first pump ( 3 ), and whose outlet side is connected with an outlet ( 15 ),   an outlet ( 15 ) for removing a diluted aqueous polymer concentrate from the device for further processing or using,   
       wherein the size of the opening(s) of the device for narrowing the cross-section ( 8 ) is such that the device for narrowing the cross-section ( 8 ) generates a pressure difference in the range of 6.9×10 5  to 1.1×10 6  Pa. 
     
     
         47 . Device according to  claim 46 , wherein the inlet ( 7 ) is selected from
 T-piece distributor,   perforated plate,   a distributor which is a hollow body comprising a plurality of perforations, wherein the stream of the aqueous base fluid circulates around the distributor and the aqueous polymer concentrate is pressed through its perforations, and   a tube distributor comprising a perforate segment, whose outer side is surrounded by a chamber comprising the inlet for the aqueous polymer concentrate, wherein the stream of the aqueous base fluid circulates through the hollow body and the aqueous polymer concentrate passes through the perforated segment into the stream of aqueous base fluid.   
     
     
         48 . Device according to  claim 46 , wherein the device additionally comprises a bypass ( 16 ), whose inlet side is connected with the connecting tube ( 2 ) between the at least one source ( 1 ) and the first pump ( 3 ) at a location before the inlet ( 7 ), and whose outlet side is connected with the connecting tube between the source ( 4 ) and the second pump ( 6 ). 
     
     
         49 . Modular, relocatable device for making an aqueous treatment fluid comprising water-soluble polymers for treating subterranean formations, characterized in that the modular, relocatable device comprises at least
 a tube ( 2 ), which comprises an inlet ( 7 ) for adding an aqueous polymer concentrate to a stream of an aqueous base fluid,   a first pump ( 3 ), whose inlet side is connected with the tube ( 2 ), and whose outlet side is connected with a device for narrowing the cross-section ( 8 ),   a device for narrowing the cross-section ( 8 ), whose inlet side is connected with the first pump ( 3 ) and whose outlet side is connected with an outlet ( 15 ),   an outlet ( 15 ) for removing a diluted aqueous polymer concentrate from the device for further processing or using   
       the size of the opening(s) of the device for narrowing the cross-section ( 8 ) is such that the device for narrowing the cross-section ( 8 ) generates a pressure difference in the range of 6.9×10 5  to 1.1×10 6  Pa. 
     
     
         50 . Modular relocatable device according to  claim 49 , wherein the modular relocatable device additionally comprises a second pump ( 6 ), whose inlet side is connected with a source for the aqueous polymer concentrate and whose pressure side is connected with the inlet ( 7 ), and wherein the device additionally comprises a bypass ( 16 ), whose inlet side is connected with the connecting tube ( 2 ) a location before the inlet ( 7 ), and whose outlet side is connected with a connecting tube between the source for aqueous polymer concentrate and the second pump ( 6 ). 
     
     
         51 . Use of an aqueous treatment fluid comprising water-soluble polymers as friction reducer, wherein the aqueous treatment fluid is obtainable by a process according to  claim 42 . 
     
     
         52 . Use of an aqueous treatment fluid comprising water-soluble polymers as thickener in enhanced oil recovery, wherein the aqueous treatment fluid is obtainable by a process according to  claim 42 .